The increasing complexity of modern electronic equipment has resulted in correspondingly complex test systems used to exercise and verify system performance of a unit under test (UUT). To accommodate the many different types of electronic systems to be tested, test equipment is built using a modular architecture. Commercially available standard and custom instrumentation modules are built on standard sized circuit boards which are combined to form a reconfigurable test system adaptable to perform specialized testing of a UUT.
The individual instrumentation cards constituting the testing system are mounted in a common card cage which provides mechanical support and electrical connections between the instrumentation cards. A rear end of each instrumentation card has signal input/output and power terminals which slide into and engage an edge connector located on a mother board mounted at the rear of the card cage.
A metal panel is mounted on the front of each instrumentation card and includes connectors for interfacing the instrumentation card to a UUT. Each instrumentation card is attached via a suitable connector either directly to a corresponding connector on the UUT or to an interface or break out box. An interface box is used to provide appropriate interconnections, testing configurations and connectors for interfacing the test system to a specific UUT. The interface box may include patching facilities to configure the various test signal input/output terminals for a specific UUT and to provide suitable connector pin-out configurations adapted for a specific UUT configuration.
The instrumentation cards are loosely held in the card cage by slides at top and bottom edges of each card. Providing a limited amount of play in mounting the circuit cards facilitates insertion of the rear edge connector of the card into the mother board and accommodates slight card positioning misalignment. Difficulty in aligning the instrumentation cards is compounded by variations between cards as a result of normal manufacturing tolerances in construction of the card, the front panel and the front connectors. As a result, the front connectors of the instrumentation cards are not precisely aligned within the card cage so that a single integrated connector cannot provide electrical connections to all the instrumentation cards. Instead, each electrical connector attaching a corresponding cable to an instrumentation card must be individually engaged with the corresponding card panel connector. Providing individual connections to each of the instrumentation cards is time consuming, error prone and increases wear to the connector.
Prior art systems which need a separate interface or break-out box to adapt the outputs from the individual instrumentation cards to a particular UUT require extra cabling and connectors between the test system and the interface box. Reconfiguring the interface box for a specific UUT configuration becomes time consuming and error prone.
The instrumentation cards used in a testing system are commercially available from a variety of vendors using industry standard circuit board sizes, rear edge pin configuration to interface with a mother board and standard front panel sizes and mounting screw placement. However, card cage depths are not standardized so that differing card cage manufacturers provide different set back distances measured from the front edge of the card cage to the front panels of the instrumentation cards. It is therefore difficult to manufacture a universal connector for attaching signal lines to the instrumentation modules. Further, to avoid damage to expensive instrumentation cards, modifications to the cards are to be avoided.
Accordingly, it is an object of the invention to provide a system for interfacing a unit under test to instrumentation and related circuit cards mounted in a card cage.
Another object of the invention is reduce the number of manual steps required to connect several card cage mounted circuit cards to a UUT.
Still another object of the invention is to eliminate intermediate jumper cables between a test system and a junction box.
A further object of the invention is provide an interchangeable input/output connector configuration capability for a test system.